Avoidance and its bi-directional relationship with conditioned fear: Mechanisms, moderators, and clinical implications.

Fear motivates different types of defensive behaviors. These behaviors are, however, not mere byproducts of fear. In this review, we highlight a bi-directional relationship between conditioned fear and instrumental defensive behavior in humans. We discuss mechanisms involved in the link from fear to goal-directed avoidance (e.g., relief, generalization), that may become habitual. These defensive behaviors may in turn reduce, preserve, or amplify fear responding (e.g., protection-from-extinction, behavior-as-information). Multiple factors moderate the bi-directional relationship. Evidence for amplifying and dampening effects of inter-individual differences (e.g., trait anxiety, distress tolerance), intra-individual states (e.g., stress), and external factors (e.g., incentives for competing behavior) on goal-directed and/or habitual defensive behavior is reviewed. However, the exact mechanisms by which these factors moderate the bi-directional relationship are still largely unknown (e.g., modulating avoidance directly vs. indirectly via conditioned fear). Finally, we discuss major implications: First, understanding factors moderating the bi-directional relationship provides insights into risk and resilience factors for anxious psychopathology. Second, specific experimental models and clinical interventions can be mapped onto distinct defensive behaviors (e.g., goal-directed vs. habitual avoidance). More precise matching will help to develop nuanced models and interventions to reduce pathological behaviors and individualize treatments.